1. Field of the Invention
The present invention relates to a communication system with a group registration function, and particularly to a communication system with a group registration function, which is capable of simply registering group members and simply selecting one of full duplex communication, full singlet (broadcast mode) communication, and half duplex communication as needed, and which is suitable for a vehicle such as a motorcycle.
2. Description of the Background Art
When a group of persons enjoy driving or touring by cars or motorcycles, the drivers or riders are, during running, required to consult with each other on where they will rest or which way they will select at a branch road or urgently transmit important communication items to each other. To meet such a requirement, it is very convenient to use communication devices mounted on vehicles. This is because the drivers or riders can consult with each other without temporary stoppage of the vehicles. From this viewpoint, various communication devices mounted on vehicles have been developed.
As one example of conventional communication devices of this type, there is known a communication device which makes communication at the same frequency in the same wave mode, for example, amateur radio transmission or personal radio transmission. Such a communication device, however, has a problem in terms of stealth. This is because when a person transmits a signal to a partner, such a signal is possibly received by a communication device possessed by a person independent of the transmitter. The communication device has another problem in terms of radio interference. This is because when a person receives a signal from a partner, an audio signal transmitted from a person independent of the receiver possibly reaches the receiver.
To solve the above-described problems, a mode called “tone squelch” permitting communication with only a group of partners previously registered, has been generally, widely used. In the case of using this mode, a person in the registered group receives and regenerates only a signal transmitted from a partner in the same registered group, and accordingly, the person in the previously registered group can make communication with only a partner in the same registered group. This makes it possible to keep good stealth, and to solve the problem of obstructing conversation due to radio interference.
Such a mode called “tone squelch”, however, has a problem that switches provided on a main body of the communication device must be operated several times (four or five times or more) in order to set the above-described mode. Such mode setting is too complicated to be used for a motorcycle.
In general, the communication type is classified into full duplex communication (two-way communication) and half duplex communication (two-way communication but single-way communication at a time). A rider in a group running by motorcycles often wants to make free two-way conversation with a specific partner (for example, a consort in the group) in the full duplex mode, and to make conversation with the other partners in the half duplex mode, as needed.
The full duplex mode allows two-way conversation just as usual telephone communication only by depressing a conversation switch once. This is convenience for the case where the communicating destination is limited to a specific person as an intercommunication system. On the other hand, in the case where a plurality of motorcycles run together, the use of the half duplex mode or a full singlet mode (broadcasting mode) is convenient. This is because a communication content to be communicated with all the riders can be simultaneously received by all the riders by use of the half duplex or full singlet mode.
The background art communication devices, however, has a problem that it is difficult to change, during communication in the full duplex mode, the communication in the full duplex mode into the communication in another mode, for example, in the full singlet (broadcast) mode or half duplex mode.
As described above, the background art communication device has the problem that since the number of operating switches for setting the mode for permitting communication with only a registered group becomes excessively large, it is cumbersome or difficult to set the mode during running of motorcycles. Another problem of the background art communication device is that since it is difficult to change, during communication in the full duplex mode, the communication in the full duplex into the communication in another mode such as the full singlet (broadcast mode) or half duplex mode, the communication device is inconvenient in that it is difficult to smoothly make communication with all the partners during communication in the full duplex mode.